Rebuilding the nation's plumbing network

For this reason, the Metropolitan Sewer District has gone beyond the usual inspection techniques. These include using TV cameras shuttled between manhole covers on dollies and visual surveys by oxygen-masked engineers. Instead, the St. Louis authorities hope infrared scanning, radar, and deflectometers (devices that put pressure on a roadway and then measure the dip) will point up the worst cracks in ancient archways as well as the cavities around them which often lead to cave-ins. Many cities are closely watching the St. Louis experiment.

''We may prove unsuccessful, but we can't afford to wait anymore for something to happen - and maybe someone to get hurt,'' says John Koeper, maintenance director for the sewer district.

* In suburban Washington, engineers are using unusual plastic liners to refurbish old sewers. Towns in Maryland's Montgomery and Prince Georges Counties admittedly don't have the most antiquated plumbing system in the US. But the Washington Suburban Sanitary Commission (WSSC) figures it can fix up old pipes for half the cost of putting in new ones.

One weapon: a felt and polyurethane tube saturated on the inside with resin. It can be slipped inside old sewer pipes. When filled with hot water, it turns inside out like a sock and cements to the duct walls, forming a plastic liner. A number of cities are now using similar systems. But probably no one has taken it as far as the WSSC, which lays 14 miles of the pipe sheathing a year. The process has long been used in repair-minded Britain, but only recently here.

* In Sacramento, engineers are lobbing numbers at woeful water mains and seaping sewers. They have been statistically mapping where the worst flaws are hiding. The reason: to determine where scarce funds can be best used. Nearly all towns, of course, keep inspection books. But some consultants consider Sacramento's dusty sewer logs and ''leak'' maps Michener-esque in thoroughness.

With the data, ''scenarios'' are worked out to help anticipate problems in the sewer system. Computers are used to create models of water flows and then to gauge where leaks may spurt.

None of this, however, will replace the field crews who visually scout for problems. Indeed, some old hands - using just their experience and a geophone (a water worker's stethoscope) - can pinpoint not only where leaks are but also their size from the sounds they make.

New tools, nevertheless, can cut down on the number of costly and irksome ''dry holes'' bored in streets in search of leaks. In a few cases, too, technology comes in handy for more than just repair work. When Sacramento water and sewer officials, for instance, meet with skepticism on the part of city politicians about the scope of municipal plumbing problems, they bring in ''dirty movies.'' These are TV tapes routinely taken of the city's buried sewer mains. What they show, often in vivid if not entertaining detail, are the piles of rubble and gaping holes in the lines - as well as an occasional rat.

Do the tapes produce the desired effect? The politicians ''at least realize what we're facing,'' Mr. Bitten says. ''They're convincing to us - and we see them all the time.''

Ultimately, though, observers agree that it will take a lot more footage, financing, and forward thinking to sort out the country's underground utility problems. But at least, they point out, a few fingers are beginning to be put in the dike. City water leaks

TThe following is a spot check of US cities and their estimated water losses

Leakage Percent of water City percentage not accounted for* Philadelphia 18.9 35.0 Boston 17.5 39.0 Buffalo, N.Y. 15.0 20.0 Houston 13.2 24.0 Chicago 12.0 (Not available) Portland, Ore. 8.5 17.0 New Orleans 7.6 8.0 Independence, Mo. 7.0 7.0 Dallas 6.6 6.6 Louisville 4.2 17.0 Tucson 3.0 5.0 Iowa City 1.5 2.0 Kansas City, Mo. 0 21.0 * Water not accounted for is due to faulty meters and/or unmetered municipal uses, such as in government buildings or for firefighting. Source: Urban Institute

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